EP1295060A1

EP1295060A1 - Tubular threaded joint capable of being subjected to diametral expansion

Info

Publication number: EP1295060A1
Application number: EP01949517A
Authority: EP
Inventors: Jean-Luc Coulon; Thierry Noel; Gabriel Roussie; Emmanuel Varenne
Original assignee: Vallourec Mannesmann Oil and Gas France SA
Current assignee: Vallourec Oil and Gas France SAS
Priority date: 2000-06-30
Filing date: 2001-06-25
Publication date: 2003-03-26
Anticipated expiration: 2021-06-25
Also published as: US20020163192A1; CN1440497A; CZ303493B6; UA73779C2; DZ3363A1; DE60108500T2; CA2410425A1; JP2004502104A; CZ2003305A3; WO2002001102A1; FR2811056A1; CA2410425C; PL198903B1; ATE287510T1; CN1289847C; BR0112096A; AU2001270654A1; JP3913170B2; EP1295060B9; PL359707A1

Abstract

The invention concerns a threaded joint to be expanded, comprising a lip (5) at the end of the male element (1) and a housing for said lip on the female element (2) to make the threaded joint capable of being sealed and of having a maximum internal passage cross-section after being subjected to diametral expansion by more than 10 %, the free male end surface (9) is socketed before expansion into a partially transverse shoulder surface (10) of the female housing through the matching rebating shapes of said surfaces and the male lip (5) outer peripheral surface (7) is arranged with little play of the internal peripheral surface (8) of the female housing (6). Such a threaded joint is particularly useful for casings and tubings used in oil wells.

Description

TUBULAR THREADED JOINT SUITABLE FOR DIAMETRIC EXPANSION

The invention relates to a tubular threaded joint capable of undergoing plastic deformation by diametrical expansion and the joint obtained after such expansion.

Known tubular threaded joints produced between two very long tubes or between a very long tube and a sleeve and used in particular to constitute columns of casing tubes (“casings”) or production tubes (“tubings”) for wells of hydrocarbons or for similar wells such as for geothermal energy.

Traditionally the wells are drilled with tools of different diameters, the top of the well being drilled using a large diameter tool, for example of the order of 500 mm, while the bottom of the well is drilled with a smaller diameter, of the order of 150 mm. The wells are therefore cased using several concentric columns all suspended from the surface, the larger diameter tubes extending from the surface to a few hundred meters deep and the smaller diameter tubes s extending from the surface to the bottom of the well. The space between casing tubes and the ground is generally cemented.

When the well is fully drilled and cased, a column of production tubes is lowered inside the column of casing tubes of smaller diameter to in particular allow the ascent of the hydrocarbons to the surface.

Equipping a well therefore leads to using a large number of tubes of different dimensions and as thin as possible so as not to require too large diameters of casing tubes close to the surface.

Given the mechanical characteristics required, the casing and production tubes are generally made of heat-treated steel and they are joined to each other by threaded joints, the thickness of the threaded joints being generally greater than that of the main part of the tubes. tubes and imposing the differences in diameters between concentric columns. The API 5 CT specification of the American Petroleum Institute thus defines tubular threaded joints between two very long tubes ("integral-joint tubing",

"extreme-line casing") and sleeved threaded assemblies comprising two threaded joints making it possible to assemble two very long tubes using a sleeve.

Numerous patents have come to perfect these threaded joints and assemblies: for example the patents FR 1,489,013, EP 0 488 912, US 4,494,777 have aimed at producing tubular threaded joints called "superior" or "premium" particularly leaktight thanks to spans of metal-to-metal sealing and to stops between male and female elements.

Very recently, new modes of use of the tubular columns of hydrocarbon wells are envisaged consisting in inflating from 10 to 20% the diameter of the tubes of the column using a ball whose passage is forced to the inside the column: see patents or patent applications WO 93/25799, WO 98/00626, WO 99/06670, WO 99/35368, WO 00/61915, GB 2344606, GB 2348657.

Such an expansion can make it possible, for example, to set up a column of casing tubes without having to cement the space between the outer peripheral surface of the tubes and the surface of the hole drilled in the ground or by lowering a column of small bulk compared to at the hole.

Such an expansion can also make it possible to seal the holes in a casing or production tube pierced by corrosion or by the friction of the drill rods or to descend into the well tubes of small dimensions which will be expanded to the desired diameter once in place.

But the expansion technique can above all make it possible to drill wells of uniform diameter over their entire length, the casing of which is produced by a column of tubes all of the same diameter, the tubes being introduced in the unexpanded state and then being expanded in situ. to the diameter of the well.

It is then possible to greatly reduce the number of tubes necessary to equip a well by eliminating the tubes of larger diameter and greater thickness, therefore the cost of the well. It may even be considered to drill the well directly with the column of casing tubes which would act as a drill string.

However, the prior art tubular threaded joints such as those according to US Pat. No. 4,494,777 do not allow such uses.

After expansion on these joints, we observe:

- A lack of sealing which in particular prevents the expansion by hydraulically pushing the ball into the column;

- an arrow from the male end towards the inside of the joint which considerably and unacceptably reduces the operational internal diameter of the column by producing an internal projection in the space defined by the operational internal diameter;

- Possibly the rupture of the lip by exceeding the deformation capacity of certain particularly stressed areas due to variations in thickness throughout the male and female elements relative to the thickness of the body of the tube.

This is why the documents cited above concerning the expansion techniques describe for the embodiments of the junctions between tubes only welded joints (coils of tubes butted together beforehand unwound from the surface) or friction joints ("briefs" ») While threaded joints are also recognized for their performance combining mechanical resistance, tightness in all operating conditions and the possibility of disassembly-reassembly several times in a row.

Note that we know from documents US 5,924,745 and WO 98/42947 threaded joints for assembling tubes called EST (expandable slotted tubings) provided with longitudinal slots allowing the diametrical expansion of tubes at the bottom of wells hydrocarbons by passing an expansion mandrel through these tubes. Such threaded joints do not target any sealing characteristic, since the tubes are provided with slots passing through the wall of the tubes and allow an external fluid. the tube (hydrocarbon from the deposit) to enter the tube to be brought up to the surface.

We have therefore sought to produce a tubular threaded joint which is capable of withstanding the expansion operation in the well and which is impermeable to liquids or even if possible to gases after said expansion operation.

We also tried to make the tubular threaded joint simple and economical to produce.

It has also been sought that the threaded joint has good metallurgical characteristics in service, therefore after expansion, in particular that it has in this state a sufficient elastic limit, that it is free of brittleness and what it presents good characteristics to cracking under stress by H2S.

According to the present invention, the tubular threaded joint capable of being expanded comprises a male threaded element with an external male thread at the end of a first tube and a female threaded element with an internal female thread at the end of a second tube.

The male threaded element comprises, beyond the male thread going towards the free end of the element, a non-threaded male lip having an outer peripheral surface and ends with a male end surface of annular shape and orientation partially transverse.

The female threaded member includes a female thread conjugate with the male thread and a female non-threaded housing for the male lip. This housing has an inner peripheral surface and a female shoulder surface of annular shape and partially transverse orientation connected to the inner peripheral surface of the second tube.

The male thread is screwed into the female thread to a position where the male end surface is engaged against the female shoulder surface.

According to a general characteristic of the invention making the tubular threaded joint capable of being leaktight and having a maximum interior passage section after having underwent a diametrical expansion in the field of plastic deformations, the male end and female shoulder surfaces have shapes which are complementary to each other before embedding the male end surface by that of female shoulder.

In addition, the outer peripheral surface of the male lip is disposed with little clearance from the inner peripheral surface of the female housing.

The embedding of the male end surface in that of the female shoulder imposes a bending moment on the free end of the male lip when the full thickness zone of the second tube located beyond the female shoulder is inclined during expansion with respect to the axis of the assembly

The embedding makes it possible to constitute on the threaded joint in the diametrically expanded state an annular sealing zone by metal / metal contact pressure between a part of the external peripheral surface of the male lip and a corresponding part of the internal peripheral surface. female housing.

The embedding also prevents any natural tendency of said free end to plunge towards the inside of the column during expansion and to protrude inside therein in the absence of such embedding.

This behavior during the expansion noted by the inventors unexpectedly will be explained in the detailed part of the description.

By small clearance between the outer peripheral surface of the male lip and the inner peripheral surface of the female housing is meant the clearances measured perpendicular to these surfaces less than or equal to 0.3 mm.

The absence of substantial radial interference between the outer peripheral surface of the male lip and the inner surface of the female housing due to this play means that these peripheral surfaces do not act as sealing surfaces on the unexpanded joint. The inventors have indeed found that a radial interference of these surfaces before expansion of the threaded joint was not necessary to obtain a tight seal after expansion. On the other hand, they have found that too large a space between these surfaces does not allow their shrinking after expansion, shrinking necessary to obtain a tight threaded joint.

Known in the prior art US Patent 4,611,838 which describes a threaded joint having a male lip in correspondence with a female housing and having an annular surface of male end comprising an annular tooth and an annular shoulder surface female having an annular groove, in abutment against each other, the male lip having a toric outer peripheral surface and the female housing having a conical inner peripheral surface.

These peripheral surfaces interfere radially at the end of screwing to form sealing surfaces, US Pat. No. 4,611,838 aimed at maximizing the radial interference of the external toric peripheral surface of the male lip with the internal conical peripheral surface of the female housing at the end of screwing (and thereby the sealing of the threaded joint) thanks to the shape of these peripheral surfaces and to the supporting effect of the lower surface of the groove for the lower surface of the tooth.

But the male end surface according to this patent is not completely embedded in that of the female shoulder of the threaded joint and therefore does not allow a bending moment to be transmitted to the free end of the male lip due to the 'free space between the upper wall of the tongue at the free end thereof and the upper wall of the groove at the bottom thereof.

Nothing in this document suggests the effects on the sealing surfaces of a diametrical expansion with plastic deformation or even that this threaded joint can undergo such an expansion successfully. The experience acquired by the inventors shows that the sealing of a threaded joint according to document US Pat. No. 4,611,838 cannot be ensured after such an expansion.

US Patent 3,870,351 has a configuration of male lip and end and female housing close to the configuration of US Patent 4,611,838, the free male end surface being convex convex and bearing against a concave convex female shoulder surface so as to produce two sets of metal-metal sealing surfaces, one at the level of the curved surfaces, the other set being disposed on the outer peripheral surface of the male lip and on the inner peripheral surface of the female housing. Such a configuration makes it possible to increase the radial interference between the peripheral sealing surfaces.

Patent application WO 99/08034 describes a threaded joint with square threads having a male lip in correspondence with a female housing and having annular surfaces of male end and female shoulder in the form of rebates in abutment and embedded one in the other. The outer peripheral surface of the male lip and the inner peripheral surface of the female housing have cylindrical parts which interfere radially with one another to form a set of peripheral sealing surfaces at the end of screwing when the male and female rebates are embedded.

Patent US 6047997 finally describes a structure of drill pipes for underground conduits for which there is no particular requirement for sealing. The male end surface according to this patent is embedded in a female shoulder surface but the figures show a large space between the outer peripheral surface of the male lip and the inner peripheral surface of the female housing.

None of these four documents cited has a structure identical to that claimed for the present invention. Neither envisages the diametrical expansion of the threaded joints they describe nor the possibility of obtaining tight threaded joints after such an expansion.

Preferably, according to the present invention, the male end surface has, for its embedding in that of the female shoulder, the form of a rebate constituted by a transverse surface on the side directed towards the inside of the threaded joint and on the opposite side of the rabbet an annular tongue projecting axially. The female shoulder surface has, to cooperate with the male end surface, the form of a rebate constituted by a transverse surface on the side directed towards the inside of the threaded joint and an annular groove on the opposite side, the transverse rebate surface male cooperating with that of female rebate and the annular tongue cooperating with the annular groove. Very preferably for the present invention, the annular walls of the groove fret those of the tongue.

Advantageously, in the assembled position, the transverse rebate surfaces on the inside of the latter are in abutment against one another. Alternatively they can simply be in quasi-contact.

Preferably also the radial thickness of the tongue of the male rebate is substantially equal to that of the transverse surface of the same rebate.

Preferably also the height measured axially of the tongue of the male rebate is substantially equal to its radial thickness.

Preferably also the external peripheral surface of the male lip and the internal peripheral surface of the female housing are cylindrical surfaces: the machining of these non-interfering surfaces is therefore particularly easy and inexpensive.

Advantageously, the thickness of the male lip is between 1/3 and 2/3 of the thickness of the first tube.

This range of male lip thickness makes it possible to ensure a critical section at the foot of the thread sufficient for adequate resistance to the axial traction of the threaded joint.

Advantageously also, the ratio between the length and the thickness of the male lip is between 1 and 4, the length of the male lip being measured to plumb with the transverse surface of the male rebate.

The minimum value of this ratio allows plastic deformation of the male lip and the female housing during expansion; these plastic deformations generate surfaces bearing one on the other with a high contact pressure and therefore the sealing of the threaded joint after expansion. The maximum value of this ratio makes it possible to avoid uncontrolled buckling of the male lip, buckling which would result in the projection of said lip inside the column of tubes.

Very advantageously, the male threaded element has a groove at the end of the thread between the thread and the male lip. This groove facilitates plastic deformation of the male lip during the expansion of the threaded joint.

Preferably, the groove has a depth substantially equal to the height of the male thread so that the bottom of the male threads ends at the bottom of the groove.

Also preferably, the groove has a length of between 2 and 8 times its depth. A length / depth ratio of less than 2 does not allow the groove to facilitate the plastic deformation of the lip. A length / depth ratio greater than 8 results in a significant risk of the material buckling towards the inside of the column during expansion.

The invention can advantageously be applied both to threaded joints with conical threads and to threaded joints with cylindrical threads with single and / or multiple stages.

Advantageously also, the first tube and the second tube have the same internal diameter both at the level of the threaded elements and at the level of the body of the tubes, which facilitates the expansion operations.

Advantageously also, it is the same for the outside diameters.

Very advantageously, the threaded joint is of the integral type, that is to say that each tube is a very long tube which has a male threaded element at one end and a female threaded element at the other end, the element male of a tube being screwed into the female element of another tube and so on to form a column.

The present invention thus aims to protect a tight threaded joint resulting from diametral expansion in the field of plastic deformations of a threaded joint as set out above. Preferably, the diametral expansion implemented is greater than 10%.

The present invention also aims to protect the threaded joints exposed above in the unexpanded or expanded state, the threaded elements of which are made of steel comprising nitrogen-avid elements making the steel not sensitive to aging by strain hardening. The steel is also heat treated to maximize its characteristics of distributed elongation. This results in good employment characteristics.

The present invention also aims to protect a process for producing a tight tubular threaded joint.

According to this method, one starts from a tubular threaded joint according to the invention described above called "initial tubular threaded joint" for which no sealing characteristic is required and this initial threaded joint is subjected to a diametrical expansion in the field of plastic deformations using an expansion ball of diameter greater than the inside diameter of the tubes of the initial threaded joint, the expansion ball being moved axially in the initial threaded joint. The male lip and the female housing are dimensioned so that the male lip and the female housing undergo first together during the passage of the ball a plastic deformation of bending while only the female housing then undergoes a plastic deformation in the opposite direction of straightening, which comes to ultimately fret the male lip through the female housing.

Preferably, the flexion of the male lip is delimited by the presence of a groove at the end of the male lip on the side of the male thread.

Also preferably, the tubular threaded joint used is of the integral type and the expansion ball is moved from the male threaded element to the female threaded element.

The figures below illustrate, without limitation, embodiments of the invention.

Figure 1 shows a threaded joint according to the invention before diametrical expansion. FIG. 2 represents the male element of the threaded joint of FIG. 1.

FIG. 3 represents the female element of the threaded joint of FIG. 1.

Figures 4 to 7 show the threaded joint according to the invention at various stages of the expansion process.

Figure 4 shows the expansion phase of the threaded joint.

Figure 5 shows the bending phase.

Figure 6 shows the recovery phase.

FIG. 7 represents the final state of the threaded joint having undergone the expansion process.

Figure 8 shows a detail of Figure 2 at the male free end.

Figure 9 shows a detail of Figure 3 at the female housing.

FIG. 10 represents a detail of FIG. 1.

FIG. 1 represents a threaded joint according to the invention comprising a male threaded element 1 disposed at the end of a first tube 11, a male element which is screwed into abutment in a female threaded element 2 disposed at the end of a second tube 12. The internal diameter of the male threaded element is equal to the internal diameter Dl of the tubes 11, 12. The external diameter of the female threaded element is also in this case equal to the external diameter DE of the tubes 11, 12 but it can to be otherwise.

The threaded joint is shown in Figure 1 in the state simply screwed in abutment before any diametrical expansion operation.

The second tube 12 as shown is a very long tube but could very well be, not shown, a sleeve provided with the female element 2 and of a second symmetrical female element of the latter screwed to a male element situated at the end of another very long tube.

The male element 1 is shown alone in FIG. 2.

It comprises a male thread 3, conical with trapezoidal threads, and is extended towards its free end by a non-threaded part constituted by a groove 21 and by a lip 5 and ends by an annular surface with male end 9.

The groove 21 has a shallow U shape.

It starts immediately beyond the thread and its depth hg is equal to the height of the thread threads 3. In this way the bottom of the groove reaches the foot of the first thread thread.

The width of the throat Ig is substantially equal to 4 times its depth hg.

Lip 5 presents:

a) an outer peripheral surface 7 of cylindrical shape,

b) an inner peripheral surface 19 which corresponds to the end zone of the cylindrical inner peripheral surface of the first tube 11,

The lip 5 therefore has a uniform thickness β [substantially equal to half the thickness e _t of the tube 11. It has a length \ _\ measured from the end of the groove to the height of the surface 15 ( defined below) substantially equal to 3 times the lip thickness β |.

The male end surface 9 forms a rebate shown in detail in FIG. 8. This rebate consists of an annular male transverse surface 15 and an annular tongue 13 projecting axially. The male transverse surface 15 is located on the side of the rebate directed towards the inside of the threaded joint.

The walls 17, 25 of the tongue 13 are not strictly parallel but converge slightly towards the free end of the tongue; these walls are therefore carried by slightly conical surfaces coaxial with the axis of the assembly and whose half-angle at the top is 1 to 2 degrees.

The radial thickness (ed) of the tongue 13 is substantially identical to that of the transverse surface 15 while the height of the tongue (hd) (or axial projection thereof) is substantially equal to the radial thickness (ed ) of the same tab.

The female element 2 is shown alone in FIG. 3.

It comprises a female thread 4 with trapezoidal threads conjugated with the male thread 3 and a non-threaded part 6 situated on the side opposite the free end of the female element relative to the female thread 4. This non-threaded part 6 forms a housing for correspond and cooperate with the lip 5 of the male element 1.

The female housing 6 has an internal peripheral surface of the cylindrical housing 8 connected on one side to the female thread 4 and on the other side via a female shoulder 10 to the cylindrical internal peripheral surface 20 of the second tube 12.

The diameter of the peripheral surface of the housing 8 is very slightly greater than the diameter of the external peripheral surface 7 of the male lip 5 so that the surfaces 7 and 8 can slide into each other with little play when screwing in. the male element in the female element, for example with a play of 0.2 mm.

The female shoulder (see FIG. 9) has an annular shoulder surface 10 which is arranged in a substantially corresponding manner and has a shape substantially corresponding to that of the male end 9. The surface 10 forms a rebate consisting of an annular surface female transverse 16 and an annular groove 14.

The female transverse surface 16 is located on the side of the rebate directed towards the inside of the threaded joint.

The groove 14 has an axial depth (Pr) slightly greater than the height of the tongue 13 so that, in the assembled position, the transverse surfaces male and female annulars 15, 16 abut one against the other while the end of the tongue 13 is not in abutment against the bottom of the groove 14 (see FIG. 10).

The walls 18, 26 of the groove 14 are not strictly parallel but converge slightly towards the bottom of the groove; these walls are therefore carried by slightly conical surfaces coaxial with the axis of the assembly and whose half-angle at the top is equal to 1 to 2 degrees like the half-angle at the top of the walls 17, 25 of tongue 13.

The radial width (Ir) of the groove is therefore not strictly constant over the entire depth of the groove; it is adapted so that the peripheral walls of the tongue 13 come into contact with the corresponding walls of the groove 14 a little before the assembly position.

This ensures both the small clearance required between the peripheral cylindrical surfaces of lip 7 and housing 8 and the hooping of the tongue 13 by the groove 14. This hooping and the abutment of the transverse surfaces 15, 16 constitute a preferred mode of ensuring the embedding of the male end surface 9 by that of the female shoulder 10.

FIGS. 4 to 7 explain the deformation phenomena which occur when a diametral expansion of the order of 15% is carried out by means of a ball on tubes assembled by the threaded joints which have just been described and which allow to obtain in the end a waterproof expanded joint.

Such deformation carried out on metallic materials leads to plastic deformations of the metal.

We thus pass for example an outside diameter of 139.7 mm (5 "1/2) on the second tube 12 upstream of the expansion and therefore in the part not yet deformed to an outside diameter of 157.5 mm (6.2 ") on the first expanded tube 11 (plumb or downstream of the outlet cone 33 of the ball). It is therefore necessary to use for the tubes a metal which accepts such plastic deformations. The plastic deformations generated increase the elastic limit of the products: a tube initially having an elastic limit of 310 MPa (45 KSI) thus sees this increase to 380 MPa (55 KSI) after deformation.

The diametrical expansion is carried out in a known manner using a ball 30 (FIG. 4) of adequate maximum diameter, the passage of which is forced through the tubes, either by pulling it using drill rods or by pushing it. for example by hydraulic pressure.

The ball has for example a biconical shape with an inlet cone 31 on which the expansion takes place, a central cylindrical part 32 and a conical outlet part 33. All the surfaces of the ball parts are connected together by spokes of suitable connections.

Patent application WO 93/25800 notably discloses angles of inlet cones particularly suitable for the diametrical expansion of so-called EST tubes for the exploitation of hydrocarbon wells.

The tubes 11, 12 having a constant cross section at their ends do not pose any particular problem during the passage of the ball provided that the deformation capacity of the metal from which they are made is sufficient.

The problems to be solved come from the fact that the threaded elements at the end of the tubes have smaller thicknesses than those at the body of the tubes and tend to deform differently between the male parts and the corresponding female parts.

These different deformations, if they are controlled by using the threaded joint according to the invention, make it possible to produce a tight threaded joint after diametral expansion having no unacceptable local relief inside the inner peripheral surface of the tubes.

The expansion process of the threaded joint can be broken down into 4 phases which are the subject of Figures 4 to 7. Although the expansion operation can quite well be carried out in the opposite direction and lead to adequate results, the preferred mode of deformation has been shown in which the ball moves from the male element 1 of the first tube 11 towards the female element 2 of the second tube 12.

a) Expansion phase on the ball cone

Figure 4 shows the threaded joint during this phase.

The expansion is carried out by the inlet cone 31 of the ball 30 and FIG. 4 shows the male 3 and female 4 threads during diametrical expansion.

In Figure 4, the inlet cone 31 of the ball 30 initiates the deformation of the male lip and the corresponding female housing area by bending them to tilt them relative to the axis of the assembly.

During this expansion phase, the reaction forces on passage of the ball 30 are gradually transferred from the first tube 11 to the second tube 12.

As a result of these reaction forces, the male lip 5 is compressed axially during this expansion phase by the annular surface of the female shoulder 10.

The end of the expansion phase corresponds to the arrival of the free end of the male element at the end of the inlet cone 31 of the ball.

b) Bending phase

During this phase, the male lip is located at the level of the central part 32 of the ball: see FIG. 5.

i) male leyre

The male lip 5 is subjected at each of its two ends to bending moments in opposite directions. The male end surface 9 is in fact embedded in the female shoulder surface 10 due to the rebates with supports 15, 16 and tongue fret system

13 / groove 14.

The embedding of the rebates forces the free end zone of the male lip 5 to follow the inclination of the zone 22 of full thickness of the female element beyond the shoulder, zone 22 which is still in progress. expansion on the inlet cone 31 of the ball and therefore creates a bending moment at this level.

The other end of the lip, on the male thread side 3, is no longer supported and, on the contrary, imposes on the lip a bending moment more opposite to that at the free end of the lip.

The bending moments of opposite sign at the 2 ends of the male lip cause the banana curvature of the male lip 5 as in FIG. 5, the outer peripheral surface 7 of the lip 5 taking a convex convex shape.

The state of axial compression of the male lip 5 at the end of the expansion phase facilitates its curvature under the effect of bending movements.

The groove 21 located between the male lip 5 and the male thread 3 plays the role of a plastic ball which accentuates the curvature of the male lip by limiting the width over which this curvature can take place.

It must however be ensured in this case that the axial compression stresses at the level of the male lip do not induce buckling of the metal 23 under the throat, which would result in a projection of the metal under the throat relative to the inner peripheral surface 19.

ii) female housing

The same flexing phenomenon occurs on the female housing.

The zone 22 of full thickness relatively rigid compared to the zones of relatively thin lip undergoes in its passage at the level of the median part an additional expansion so that the internal diameter of the zone 22 becomes greater than that of the median zone 32 of the ball. The phenomenon of additional expansion is described in document WO 93/25800.

c) Recovery phase

This phase illustrated in FIG. 6 corresponds to the passage of the zone 22 of full female thickness over the middle part 32 of the ball 30.

i) female housing

The bending generated in the previous phase tends to be reduced to zero under the effect of tension and circumferential stresses, which generates a state of axial stresses of reverse bending with respect to the curvature, thus producing straightening.

The bending moment generated by these constraints is proportional to the thickness of material upstream of the straightening. When arriving at the tube 12 in full thickness (zone 22), the bending moment is then not sufficient to straighten the inner peripheral zone of the female housing which then tends to plunge towards the axis of the product. This behavior is manifested by a local decrease in the outside diameter of the tube 12.

ii) male leyre

As the female part straightens, the difference in axial size which was generated by the bending decreases. The male lip 5 therefore gradually loses its state of compression. This continues with the separation of the surfaces 15, 16 initially in abutment. This phenomenon is reinforced by "the dip" of the inner peripheral surface 8 of the female housing which produces an opening effect of the stops 15, 16.

The banana deformation imposed in the previous phase is retained.

d) Final state

Figure 7 shows the final state of the threaded joint after the passage of the ball. The state of circumferential stresses generated by the expansion leads to hooping of the outer peripheral surface 7 of the male lip by that of the inner 8 of the female housing. We can then speak of self-hooping of the surfaces 7, 8 of the threaded joint in the expanded state, which ensures sealing. The male lip 5 does not dive towards the axis, because the offset imposed by the embedding of the rebates 9, 10 has generated enough plastic deformations.

The elastic return of the elements of the threaded joint after passage of the ball is negligible compared to the plastic deformations involved.

The radial hooping induces a contact pressure of several tens of MPa, sufficient to ensure a seal against pressures inside or outside the threaded joint.

A seal is moreover necessary when the expansion is carried out by hydraulically pushing the ball 30 under a pressure of 10 to 30 MPa, any leak at the level of the already expanded joints preventing the penetration of the ball further into the column and consequently blocking the expansion process.

Note that in the final state, it may very well happen that the tongue 13 no longer rests in the groove 14 and in particular no longer on the inner wall 18 of the groove.

The characteristics which are the subject of claim 1 and of the claims dependent thereon make it possible to obtain the desired results.

A male end surface 9 does not allow embedding with that of female shoulder 10 causes a plunge of this end during the straightening phase which sees the separation of the transverse surfaces 15 and 16 initially in abutment and it follows a unacceptable projection of the lower end of the male lip inside the column. The column then no longer allows to descend devices or tools of a given size.

The excessive play between the peripheral surface 7 of the male lip 5 and the peripheral surface 8 of the female housing on the threaded joint before expansion would not allow the hooping of these surfaces at the end of the expansion operation. Radial interference between these surfaces in the initial state before expansion is liable to hinder differential deformations (curvature, straightening) between these surfaces during expansion operations, differential deformations making it possible to hoop these surfaces at the end of the operation. expansion.

The preferred form of annular rebate with transverse surfaces 15, 16 and tongue 13 / groove 14 system makes it possible to prevent the free male end from diving, during expansion, but is only one example of a possible embodiment. for recessed surfaces 9, 10, other modes being possible giving the same result.

Male lip 5 too thin, β thick | less than a third of the thickness e _t of the tubes 11, 12 does not make it possible to produce an effective stop at the level of the transverse surfaces 15, 16.

If the thickness β | on the contrary, the male lip 5 is greater than 2/3 of the thickness e _t of the tubes 11, 12, the thickness of the tube 12 at the level of the female housing zone leads to a critical cross section of female thread 4 that is too small and therefore insufficient tensile strength of the threads.

The length / thickness ratio of male lip 5 governs the compression and bending behavior of lip 5.

A male lip 5 of length l | less than its thickness β does not allow sufficient bending of the peripheral surface 7 of the male lip 5 and / or the straightening of the peripheral surface 8 of the female housing.

A male lip 5 of length l | greater than 4 times its thickness e ι may cause buckling of the male lip and an internal projection thereof on the thread side.

This effect is accentuated by the presence of a groove 21 between male thread 3 and male lip 5.

This is why the groove preferably has a depth limited to a height of the thread and a length limited relative to its depth. Example of realization

- outside diameter of tube 139.7 mm and a nominal thickness e _t 7.72 mm (5 "x ^1/2 17.00 Ib / ft) carbon steel treated for a minimum yield point of 290 MPa (42 KSI):

The chemical composition of the steel and its heat treatment are adapted to obtain the highest possible ductility characteristics and more particularly high characteristics of distributed elongation before necking A _R during the tensile test (A _R greater than or equal 15% for example).

For example, choose a steel with a sufficiently low carbon content, close to 0.14% (by weight), with a relatively high manganese content, of the order of 1% and comprising an addition of aluminum capable of fixing the residual nitrogen from steel.

An Al content of 0.035% for a nitrogen content of 0.010% is entirely suitable insofar as the steel is heat treated by annealing or by quenching followed by tempering so that the addition of AI is effectively able to fix nitrogen. Other chemical elements known to fix nitrogen can also be used jointly or in place of aluminum.

Such a chemical composition which aims to eliminate the contents of free interstitial atoms such as those of nitrogen also makes the steel insensitive to the harmful phenomenon of aging after work hardening which also deteriorates the ductility characteristics.

The steel can be in the annealed state (normalization annealing or stress relief annealing after cold working for example) or in a structurally equivalent state.

Integral threaded joints according to the invention

• 3.4 conical threads (taper = 12.5% on the diameter) with trapezoidal threads of radial height 1 mm and axial pitch 4 mm • male lip 5 of cylindrical shape • thickness βι of male lip 3,2 mm (41% of the thickness of the tube)

• length l | male lip = 11.5mm

• groove 21 with depth hg 1 mm and length Ig 4 mm between male thread end 3 and male lip 5 • male end surface 9 with a tongue 13 of axial height 1.8 mm and radial thickness 1.8 mm

• tensile strength of the threaded joint ≥ 50% of the tensile strength of each of the tube bodies 11, 12.

- Results after expansion of the tube column:

outer diameter of the tubes 11, 12 = 157.5 mm (6.2 ") tube thickness: 7.2 mm elastic limit of the tubes ≥ 415 MPa (60 KSI) • hardness ≤ 22 HRc (maximum value NACE MR specifications 01 75) passages satisfying the following tests carried out in the expanded state and in the expanded state + aged

→ - burst test under internal pressure

→ - collapse test under external pressure ("collapse") → - Charpy V impact test

→ - SSC crack resistance test using H ₂ S (SSC: "Sulfide stress cracking") according to NACE TM 01-77 specification

Note: NACE = National association of Corrosion Engineers (USA).

The description of the embodiments presented does not exclude that the protection granted to the present invention may apply to embodiments not explained in detail but covered by the present invention.

Claims

1) Tubular threaded joint capable of being expanded comprising a male threaded element (1) at the end of a first tube (11) and a female threaded element (2) at the end of a second tube (12), the threaded element male comprising, going towards the free end of said male element, a male thread (3) and a male lip (5) which has an outer peripheral surface (7) and ending transversely with respect to the axis of the joint threaded by a surface male end (9) of annular shape, the female threaded element (2) comprising a female thread (4) corresponding to the male thread (3) and a non-threaded part (6) of female housing for the male lip, this female housing comprising an inner peripheral surface (8) and a female shoulder surface (10), annular and of transverse orientation, the male thread (3) being screwed into the female thread (4) to a position where the annular end surface male (9) is engaged against the female shoulder surface (10), characterized in that, in order to make said threaded joint capable of being leaktight and of presenting a maximum interior passage section after having undergone diametrical expansion in the field of plastic deformations, the annular male end (9) and female shoulder (10) surfaces have, prior to expansion, shapes that are complementary to each other, embedding the male end surface (9) by that female shoulder (10) and in that the outer peripheral surface (7) of the male lip (5) is arranged with little clearance from the inner peripheral surface (8) of the female housing (6).

2) tubular threaded joint according to claim 1 characterized in that the male end surface (9) has the shape of a rebate constituted by a transverse surface (15) on the inner side of the threaded joint and on the opposite side of the rebate by an annular tongue (13) projecting axially and in that the female shoulder surface (10) has a form of rebate constituted by a transverse surface (16) on the side directed towards the inside of the threaded joint and by a groove (14) annular on the opposite side, the transverse surface of male rebate (15) cooperating with the transverse surface of female rebate (16) and the tongue (13) cooperating with the groove (14).

3) tubular threaded joint according to claim 2 characterized in that the annular walls of the tongue (13) and of the groove (14) are arranged so that in the assembled position of the threaded joint, the annular walls (18, 26) of the groove radially fret those (17, 25) of the tongue. 4) tubular threaded joint according to claim 3 characterized in that the annular walls (17, 25) of the tongue (13) are slightly conical and converge towards the free end of the tongue and in that the annular walls (18, 26) of the groove (14) are slightly conical and converge towards the bottom of the groove, the inclination of the groove walls being equal to that of the tongue walls.

5) tubular threaded joint according to any one of claims 2 to 4 characterized in that the transverse male and female rebate surfaces (15, 16) are in abutment against one another.

6) tubular threaded joint according to any one of claims 2 to 5, characterized in that the radial thickness (ed) of the tongue (13) is substantially equal to that of the transverse surface (15) of the male rebate ( 9).

7) tubular threaded joint according to any one of claims 2 to 6, characterized in that the height measured axially (hd) of the tongue (13) is substantially equal to its radial thickness (ed).

8) Tubular threaded joint according to any one of claims 1 to 7, characterized in that the external peripheral surfaces (7) of male lip and internal (8) of the female housing are cylindrical.

9) tubular threaded joint according to any one of claims 1 to 8 characterized in that the male lip (5) has a thickness (β |) between 1/3 and 2/3 of the thickness of the first tube (11 ).

10) Tubular threaded joint according to any one of claims 1 to 9 characterized in that the lip (5) has a length {I and a thickness (e,) such that the ratio of length to thickness of lip is between 1 and 4.

11) Tubular threaded joint according to any one of claims 1 to 10 characterized in that the male element (1) has a groove (21) at the end of the male thread (3) between thread and male lip (5). 12) Tubular threaded joint according to claim 11 characterized in that the groove (21) has a depth (hg) equal to the height of the male threads (3).

13) Tubular threaded joint according to claim 11 or claim 12 characterized in that the groove (21) has a length (Ig) and a depth (hg) such that the lip length is between 2 and 8 times its depth.

14) Tubular threaded joint according to any one of claims 1 to 13 characterized in that the first tube and the second tube (11, 12) have the same internal diameter (Dl) both at the level of the threaded elements (1) (2 ) only from the body of the tubes.

15) Tubular threaded joint according to claim 14, characterized in that the first tube and the second tube (11, 12) have the same external diameter (DE), both at the level of the threaded elements (1, 2) and of the body of the tubes.

16) Tubular threaded joint according to claim 14 characterized in that it is of the integral type.

17) Sealed tubular threaded joint characterized in that it results from a tubular threaded joint according to any one of claims 1 to 16 after a diametrical expansion in the field of plastic deformations.

18) tight tubular threaded joint according to claim 17 characterized in that the diametrical expansion undergone by the tubular threaded joint is greater than 10%.

19) Tubular threaded joint according to any one of claims 1 to 18, characterized in that the threaded elements (1) (2) are made of steel comprising nitrogen-avid elements making the steel insensitive to aging by work hardening and in that the steel is heat treated to maximize its distributed elongation characteristics.

20) A method of producing a tight tubular threaded joint characterized in that one starts from a tubular threaded joint according to any one of claims 1 to 16 called "initial tubular threaded joint" for which no sealing characteristic is not required, in that this initial threaded joint is subjected to a diametrical expansion in the field of plastic deformations using an expansion ball (30) of diameter greater than the internal diameter (Dl) of the tubes of the initial threaded joint, ball which is displaced axially in the initial threaded joint, the male lip (5) and the female housing (6) being dimensioned so that the male lip and the female housing first undergo together together during the passage of the ball a plastic deformation of bending while only the female housing then undergoes a plastic deformation in the opposite direction of straightening, which ultimately comes to hoop the male lip through the female housing.

21) A method of producing a tight tubular threaded joint according to claim 20, characterized in that the flexion of the male lip (5) is delimited by the presence of a groove (21) at the end of the male lip on the male thread side.

22) A method of producing a tight tubular threaded joint according to claim 20 or 21, characterized in that the tubular threaded joint used is of the integral type and in that the expansion ball (30) is moved from the 'male threaded element (1) to the female threaded element (2).